The present invention relates to drive systems for adjusting the position of a remotely controlled electrically operated automotive rearview mirror.
It is known in the prior art to adjust the position of an outside rearview mirror by means of electrically driven rotatable nuts which cause longitudinal non-rotary movement of two screws which engage the mirror backing plate to cause it to pivot about each of two mutually perpendicular axes. The rotatable nuts may be driven by either a single motor-driven worm gear which selectively pivots into engagement with one or the other of the nuts or by two sets of motors and worm gears.
Representative of such prior art patents are U.S. Pat. Nos. 3,972,597, 4,041,793, 4,273,417 and 4,324,454.
It is also known to provide an override feature by which the motor is permitted to continue to run after the mirror has reached the limit of its movement, or, conversely, to permit the mirror to be manually shifted when the motor is not operating. Such override feature has been achieved, for example, by use of a split nut which permits the nut to rotate without causing longitudinal movement of the screw or permits the screw to move longitudinally without rotation of the nut. The segments of the split nut are resiliently biased in a radially inward direction to normally maintain a driving engagement with the threads of the screw. However, in an overload condition, the nut segments resiliently yield radially outwardly to disengage the driving relationship between the screw and nut threads. Exemplary of such a split nut is the drive system found in the aforementioned U.S. Pat. No. 4,041,793.
The present invention is directed to the creation of an alternative and improved override construction and to the provision of a screw and nut drive system which operates smoothly and uniformly irrespective of the angle of the mirror and the degree of travel of the mirror along its arc of pivotal movement.
The foregoing objects have been accomplished by the use of a three-piece assembly comprising a worm gear-driven pinion gear having a spherical socket which receives a ball-shaped drive nut splined for co-axial rotation with the pinion gear, and internally threaded to receive a screw member having radially inwardly and resiliently yieldable male thread segments. The ball-socket relationship of the pinion gear and nut permit the axis of the nut, and therefore the axis of the screw, to pivot or skew relative to the fixed axis of the pinion gear, while the splined connection between the spherically socketed bore of the pinion gear and the ball-shaped exterior of the nut permit uniform simultaneous rotation of such members whether their axes are coaxial or skewed. This feature permits the connection of the screw to the mirror to follow the arcuate travel of the mirror as its position is adjusted by the screws, with a smooth and uniform driving relationship irrespective of the angle of the mirror.